
async function async1(){
    console.log("async1 start")
    var a =  await async2()
    console.log(a)
    var b = await async3()
    console.log(b)
    console.log("async1 end")
}

async function async2(){
    // async 标识的函数，返回一个promise
    return 'aaa'
}

async function async3(){
    return 'bbb'
}

async1()

new Promise(function(resolve){
    console.log("promise start")
    resolve(111)
}).then(function(value){
    console.log("promise then 1",  value)
    return 222
}).then(function(value){
    console.log("promise then 2", value)
})
console.log("script end")
